Signaling events and molecules implicated in granule exocytosis in cytotoxic lymphocytes remain poorly characterized despite the central role that this effector mechanism plays in tumor and viral immunity. This study is aimed at identifying critical regulatory molecules and determining their role in regulation of lytic granule release. A functional genomics approach employing a partially automated expression cloning method will be used for this purpose. Compared to other expression cloning strategies, sib selection screening method outlined here allows more efficient identification of molecules of interest. Pools of indexed cDNA from a human brain library are already available, a human activated T cell library will be picked and pooled, and an NK cell line to be used as reporter of cytotoxic lymphocyte degranulation has been defined. Identification of granule exocytosis inducers will promote a better understanding of the regulation of cytotoxic function in CD8+ T cells and NK cells. The findings originating from this study would potentially allow modulation of cytotoxic effector function during lymphocyte response to tumors and viruses. [unreadable] [unreadable]